From the aspect of cost versus flexibility, the market for non-volatile memory cell devices can be divided into three major sections, as follows. A first section covers the so-called MASK ROM products, which are low in cost, but also low in flexibility of application since the information loaded into the memory cells cannot be modified later.
The second section covers the EPROM and OTP products, whose cost is significantly higher than that of the ROM products, but whose flexibility is much higher in that they can be programmed by the customer. EPROM products are encapsulated into packages having a transparent lens to radiation whereby the memory cells can be erased, since the cells are responsive to that radiation. This is not feasible with OTP products after they have been programmed and packaged. Furthermore, EPROM products require that their packages be disconnected from the rest of the system, before they can be erased.
The third major section covers the so-called FLASH products, whose memory cells can be modified electrically for a large number of times, thereby affording enhanced flexibility. However, this very flexibility encourages manufacturers to plan ever more complex functions for the devices, thereby facing increased costs which are bound to be high compared to those of the other products.
There are applications, however, which demand a large number of functions of the device, as well as high performance, along with ease of programming. The latter being a feature which is seldom necessary or only occasionally put to use over the device lifespan.